1. Field of the Invention
The present invention relates to a dc brushless electromagnetic rotary machine, such as a dc electric motor or, a dc electrical generator, for transducing electrical energy into mechanical energy, or vice versa.
2. Description of the Prior Art
With a conventional dc electric motor, for example, a combination of brushes and commutators has often been used for mechanically switching in direction the current directed to coil windings of armatures involved for continuous generation of torque in a certain angular direction. Rotary electric machines of such a type are however, disadvantageous in that the frictional contact of the brushes with the circumferential surface of the commutators, result in generating mechanical and electrical noises including mechanical vibrations and riples, which are significant disadvantages degrading the performance of the machines.
In the prior art also, there are brushless motors of the type which have a sensor, such as a photosensitive device, a Hall generator, together with electronics adapted to sense the angular position of a rotor so as to switch the current flowing through armature windings to generate a continuous torque in an intended angular dierction of a rotary member. The motors of that type are advantageous in including no frictional contact member such as brushes and commutators, being free from the disadvantages as caused in the motors discussed in the preceding paragraph. The electronics circuitry used in the prior art brushless motors gives rise to complexity in circuit configuration of the motors and hence expensiveness in price, and may also be affected by warm or hot environment, under about 70 degrees centigrade or more, for example.
With conventional dc electric generators, the same difficulties arise since they have the same structural features as that of the motors. This can easily be seen from the fact that, for example, driving a rotor of a dc motor by any driving means will make it function as a generator to produce electric energy induced across its armature windings.